1 Field of the Invention
The present invention relates to medical devices and more particularly, to a lead body for a medical lead and a method for constructing a lead body.
2 Discussion of the Related Art
A variety of medical electrode catheters are available today for the diagnosis and treatment of various disorders of the cardiovascular and neurological systems. These electrode catheters can be used to sense electrical activity within the body and to deliver different forms of energy to stimulate, ablate, cauterize or pace. Examples of medical catheters using electrodes include permanent and temporary cardiac pacing leads, electrophysiologic (EP) catheters, electrocautery probes and spinal stimulation catheters. Generally, for all applications, a reduced diameter lead is desired to limit the negative steric effects of lead implantation. Therefore, a need exists for a reduced diameter lead to reduce the negative effects of lead implantation.
In addition, lead size can prevent access to certain tissues and structures. In the case of neurostimulation, spinal cord stimulation may have a limited effectiveness for certain pain conditions. In many cases where spinal cord stimulation is inadequate, spinal or peripheral nerves must be specifically stimulated to provide pain relief. However, access to spinal and peripheral nerves is limited because of the limited space for lead placement within the intervertebral foramin. Therefore, with existing technology, access to certain nerves is best accomplished using a laminectomy procedure. In a laminectomy procedure, a portion of a vertibrae's lamina is surgically removed to allow placement of an electrode adjacent to the target nerve. The surgery frequently results in significant scarring and patient discomfort. Therefore, a need exists for a method to manufacture of a reduced diameter body lead to provide improve access for nerve stimulation.
Procedurally, spinal or peripheral nerve stimulation is more challenging than spinal chord stimulation. The spinal and peripheral nerves branch off of the spinal chord through the transverse foramen of the vertebrae. Spinal and peripheral nerve stimulation is necessary when a region of the body is affected that cannot be effectively stimulated via the spinal cord. To stimulate these nerves, a lead is inserted through the epidural space along the spinal chord and then turned laterally outward to track the branching nerves. Tracking these nerves requires a lead having a significantly smaller diameter than conventional stimulation leads. Further, in deep brain stimulation, a reduced diameter lead may provide for less traumatic placement of electrodes as well as more precise electrical stimulation by allowing electrode placement directly adjacent to remote target locations within the brain. Therefore, a need exists for the manufacture of a reduced diameter lead to improve access in neurological applications.
In cardiac applications, a reduced diameter leads may provide access to locations within the heart and veins that would not otherwise accessible. In addition, smaller leads allow more efficient valve function than their standard diameter counterparts when the lead passes through the valves in the heart. Further, smaller leads allow access to smaller veins without compromising blood flow. Thus, a need exists for a reduced diameter lead configured for cardiac pacing.
Prior methods for the manufacture of lead bodies either wound heated conductors into insulating material and then passed the lead bodies through a smoothing dye or wound conductors over an inner insulator and then extruded an outer insulator over the conductors. These methods do not allow for the precise control of variables such as conductor positioning and pitch during manufacture because the methods may permit the conductors to float during manufacture. Imprecise positioning can result in electrical contact between adjacent conductors resulting in the particular lead body having to be discarded. Therefore, a need exists for a method that allows for more precise control and tighter tolerances during manufacture. Further, these methods have a tendency to destroy outer coverings that may be present on the wires during manufacture. Therefore, a need also exists for a method of forming a lead body that does not destroy the integrity of coverings, such as for example insulators, during manufacture.
The present invention meets the above needs and provides other improvements and advantages that will be recognized by those skilled in the art upon review of the following description and drawings.